In an automatic analyzer, a cuvette is repetitively irradiated with light, the light that has passed through the cuvette is repetitively detected, and the measured value of a measurement item is calculated using the average value of detected output values. The sampling window of output values to be used to calculate the average value is set within a predetermined time range.
In recent years, to do inspection by separating detection target molecules using magnetic particles, there has been proposed an automatic analyzer including magnets that apply magnetic fields to a reaction liquid in a cuvette. The magnets are arranged so as to make the flux densities of magnetic fields almost even in the reaction liquid in the cuvette. In some cases, however, magnetic separation does not spatially evenly progress in the cuvette because of rotational motion of a reaction disk, positional shifts of magnets, and the like. The phenomenon that magnetic separation does not spatially evenly progress will be referred to as a fluctuation of magnetic separation hereinafter. When a fluctuation of magnetic separation occurs, the accuracy of a measurement result degrades.